When you square $-3$, you multiply $-3$ by itself:

$(-3)^2 = (-3) \times (-3) = 9$

So, $-3$ squared is 9.

Would you like a more detailed explanation or have any further questions?

Here are 5 related questions for you:

1. What is $(-5)^2$?
2. How do negative numbers behave when raised to even powers?
3. What is the difference between $(-3)^2$ and $-3^2$?
4. What is $3^2$ and how is it different from $(-3)^2$?
5. How do you square a number in algebra?

Tip: When squaring a negative number, remember that two negatives make a positive!